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Wow, this is fascinating! Wildly starforming dwarf galaxy NGC 4449 (which is, however, sitting inside a huge halo of old stars) is hungrily interacting with an even smaller dwarf galaxy made up of old stars, sucking it clean of gas in the process (and being about to incorporate its stars). The stolen gas falls onto NGC 4449, thereby fuelling furious star formation inside "the galactic culprit".

This picture may very well be a repeat, but there are Sunday repeats of our usual APODs, and today is Sunday, so why not a repeat of a found image?

Natali Anderson of Sci News wrote:
LEDA 3087775, also known as SDSS J162702.55+432833.9 or 2MASX J16270254+4328340, is a faint and diffuse elliptical galaxy. It lies approximately 500 million light-years away in the constellation Hercules.

The galaxy is a member of Abell 2151 (also known as the Hercules cluster), a cluster of about 250 galaxies.

According to astronomers, LEDA 3087775 is likely the aftermath of an ancient galactic collision.

Two Milky Way-like spirals swirled together for millions of years....

So maybe this is what the collisional product of the Milky Way and the Andromeda galaxy will look like in a number of billion years from now?

The NGC 1760 complex is the second largest emission nebula in the Large Magellanic Cloud, after the Tarantula Nebula. It doesn't get nearly as much attention as it deserves, so I want to thank you very much for your fine picture, José Joaquin Pérez!

Messier 61 is one of the largest members of the Virgo Cluster, which is made up of more than a thousand galaxies, and is itself at the centre of the Virgo Supercluster — to which our Milky Way also belongs. This dazzling beauty was first discovered in 1779, and it has been capturing astronomers’ interest ever since. Set against a dark sky littered with galaxies, this image shows the awe-inspiring M61 in its full glory — even at its distance of over 50 million light-years.

This image was taken as part of ESO’s Cosmic Gems Programme, an outreach initiative to produce images of interesting, intriguing or visually attractive objects using ESO telescopes, for the purposes of education and public outreach. The programme makes use of telescope time that cannot be used for science observations. In case the data collected could be useful for future scientific purposes, these observations are saved and made available to astronomers through ESO’s Science Archive.

Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk. — Garrison Keillor

It might appear featureless and unexciting at first glance, but NASA/ESA Hubble Space Telescope observations of this elliptical galaxy — known as Messier 105 — show that the stars near the galaxy’s centre are moving very rapidly. Astronomers have concluded that these stars are zooming around a supermassive black hole with an estimated mass of 200 million Suns! This black hole releases huge amounts of energy as it consumes matter falling into it and causing the centre to shine far brighter than its surroundings. This system is known as an active galactic nucleus.

Hubble also surprised astronomers by revealing a few young stars and clusters in Messer 105, which was thought to be a “dead” galaxy incapable of star formation. Messier 105 is now thought to form roughly one Sun-like star every 10 000 years. Star-forming activity has also been spotted in a vast ring of hydrogen gas encircling both Messier 105 and its closest neighbour, the lenticular galaxyNGC 3384.

Messier 105 was discovered in 1781, lies about 30 million light-years away in the constellation of Leo (The Lion), and is the brightest elliptical galaxy within the Leo I galaxy group.

Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk. — Garrison Keillor

It might appear featureless and unexciting at first glance, but NASA/ESA Hubble Space Telescope observations of this elliptical galaxy — known as Messier 105 — show that the stars near the galaxy’s centre are moving very rapidly. Astronomers have concluded that these stars are zooming around a supermassive black hole with an estimated mass of 200 million Suns! This black hole releases huge amounts of energy as it consumes matter falling into it and causing the centre to shine far brighter than its surroundings. This system is known as an active galactic nucleus.

Hubble also surprised astronomers by revealing a few young stars and clusters in Messer 105, which was thought to be a “dead” galaxy incapable of star formation. Messier 105 is now thought to form roughly one Sun-like star every 10 000 years. Star-forming activity has also been spotted in a vast ring of hydrogen gas encircling both Messier 105 and its closest neighbour, the lenticular galaxyNGC 3384.

Messier 105 was discovered in 1781, lies about 30 million light-years away in the constellation of Leo (The Lion), and is the brightest elliptical galaxy within the Leo I galaxy group.

Interesting. Is that red thing at upper left a jet from the black hole?

It is not obvious from the picture that M105 contains any young stars. By what means did Hubble discover them?

Hundreds of astronomical objects are visible in this ESO Picture of the Week, including star clusters, nebulae, dust clouds, and other galaxies — most notably the Large and SmallMagellanic Clouds, visible to the upper right. However, something much closer to home is vying for our attention. To the far right of the image, a silver arc streaks across the sky. This arc is actually composed of two closely-spaced lines, caused by sunlight bouncing off the antennae of two Iridium communication satellites currently orbiting the Earth.

It may be empty now, but this dry, barren section of the Chilean Atacama Desert will soon be bustling with activity. The site has been selected to host the southern part of the Cherenkov Telescope Array (CTA), a remarkable array of 99 antennas that will gaze up at this incredible sky in search of high-energy gamma rays. Gamma rays are a type of electromagnetic radiation that is emitted by the hottest and most powerful objects in the Universe — supermassive black holes, supernovae, and possibly remnants of the Big Bang itself.

However, the Earth’s atmosphere prevents gamma rays from reaching its surface, so rather than hunting for these rays directly the CTA will observe something known as Cherenkov radiation — ghostly blue flashes of light produced when gamma rays interact with particles in our atmosphere. Pinpointing the source of this radiation allows each gamma ray to be traced back to its cosmic source. Just like its neighbour, ESO’s Very Large Telescope, the CTA requires a dry, isolated location to do its work successfully — and for this the Atacama is perfect.

Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk. — Garrison Keillor